The present invention relates to a magnetic recording medium and a magnetic recording device that are suitable for high-density recording.
In recent years, along with the development of the information processing technique, there has been an increase in the kinds and amounts of information to be processed by computers, and for this reason, studies and developments have been extensively made so as to provide magnetic recording devices having a greater memory capacity, that is, magnetic recording devices capable of performing a high-density recording operation.
The studies and developments, which have been made to obtain magnetic recording devices capable of performing a high density recording operation, relate to both the magnetic head and the magnetic recording medium. For example, with respect to the magnetic head, a spin valve head, which is one type of a GMR head, has been developed as a magnetic head that is suitable for high-density recording and is capable of replacing conventional inductive heads. With respect to the magnetic recording medium, for example, a medium having the following construction has been proposed as a modified medium of a conventional magnetic recording medium having a construction in which a Cr base film, a Co alloy magnetic layer and a protective film are stacked on a non-magnetic support member.
As illustrated in FIG. 6, Japanese Patent Application Laid-Open (JP-A) No. 6-243456 has disclosed a magnetic recording medium having a construction in which an NiFe base layer 22, a Cr base layer 23, a CoCrTa magnetic layer 24 and a protective film 25 are stacked on an Al substrate 21. Moreover, as illustrated in FIG. 7, Japanese Patent Application Laid-Open (JP-A) No. 7-169037 has disclosed a magnetic recording medium having a construction in which a Cr base layer 32, a Co-based alloy magnetic layer 33, an NiFe layer 34 and a protective film 35 are stacked on an NiPxe2x80x94Al substrate 31.
In order to provide high-density recording, it is necessary to increase the S/N ratio of a magnetic recording medium, and for this purpose, it is necessary to miniaturize the size of grains constituting the recording layer. However, when the grain size is miniaturized, a problem arises, in which there is degradation in the thermal stability of recorded information (the recorded information tends to be lost).
Here, as illustrated in FIG. 6, in the case of a construction in which a soft magnetic material layer (NiFe base layer 22) is placed beneath a recording layer (CoCrTa magnetic layer 24), since a leakage magnetic flux from a transition area of the recording layer is short-circuited by the soft magnetic material layer (referred to as a keeper layer), there is a great reduction in the demagnetization field of the transition area, with the result that the thermal stability of recorded information can be improved. In other words, this construction makes it possible to compensate for the degradation in the thermal stability occurring due to the miniaturization of the grain size of the recording layer for achieving a high S/N ratio.
However, the application of this construction causes a reduction in the Hc of the recording layer, resulting in failure to provide a high S/N ratio.
It is an object of this invention to provide a recording magnetic medium which has a high Hc, and exhibits superior thermal stability.
The inventors of the present invention have studied hard so as to solve the above-mentioned problems and found that it is possible to provide a recording magnetic medium which has a high Hc, and exhibits superior thermal stability by placing a seed layer made of a non-magnetic material that is mainly composed of Cr between a so-called keeper layer and a non-magnetic support member.
In other words, the magnetic recording medium of the present invention is characterized by a construction in which on a non-magnetic support member are successively stacked a seed layer made of a non-magnetic material that is mainly composed of Cr, a keeper layer made of an NiFe-type soft magnetic material, an intermediate layer made of a non-magnetic material that is mainly composed of Cr and a recording layer made of a magnetic material that is mainly composed of Co.
Moreover, the magnetic recording medium of the present invention is characterized in that the non-magnetic material forming the seed layer includes at least one kind of or two or more kinds of elements selected from the group consisting of Mo, W, V, Nb, Ta, Ti, Zr and Zn.
Furthermore, the magnetic recording medium of the present invention is characterized in that the seed layer has a film thickness of not more than 50 nm.
The magnetic recording medium of the present invention is also characterized in that in the recording layer, a value obtained by multiplying the remanent magnetic flux density by the film thickness is set to not more than 120 Gxcexcm.
Moreover, the magnetic recording medium of the present invention is characterized in that the value obtained by multiplying the remanent magnetic flux density by the film thickness in the recording layer is greater than a xc2xd of a value obtained by multiplying the remanent magnetic flux density by the film thickness in the keeper layer, and is also smaller than 3 times the value.
Furthermore, the magnetic recording medium of the present invention is characterized in that the non-magnetic material forming the intermediate layer includes at least one kind of or two or more kinds of elements selected from the group consisting of Mo, W, V, Nb, Ta, Ti, Zr and Zn.
The magnetic recording medium of the present invention is characterized in that the intermediate layer has a film thickness of 5 to 100 nm.
Moreover, the magnetic recording medium of the present invention is characterized in that a carbon-type protective film is further formed on the recording layer.
Furthermore, the magnetic recording device of the present invention is characterized by including any one of the above-mentioned magnetic recording media and a head of a magneto resistance effect type.